Please help me with this homework

Twice the sum of a number and 4 is equal to three times the difference of the number and 7. find the number.

What is the 17th term in the arithmetic sequence in which a6 is 101 and a9 is 83

Which sum or difference identity would you use to verify that cos (180° - q) = -cos q? a.) sin (a -b) = sin a cos b – cos a sin b b.) cos (a -b) = cos a cos b – sin a sin b c.) cos (a -b) = cos a cosb + sin a sin b d.) sin (a + b) = sin a cos b + cos a sin b